The present invention relates generally to a method and apparatus for removing contaminants from groundwater and, more particularly, to an in situ sparging method and apparatus for removing volatile organic compounds (VOCs) from groundwater.
Contamination of the phreatic zone, also known as the zone of saturation, or groundwater with potentially hazardous materials is a common problem facing industry, the government, and the general public. The most common type of VOC pollutants are petroleum-based products. Frequently, as a result of spills, leakage from storage facilities, or surface discharges, contaminants percolate into groundwater, thereby posing a threat to drinking water supplies.
While groundwater is not as susceptible to pollution as surface water, once polluted, its restoration is difficult and long term. Typically, contaminated groundwater is removed from the phreatic zone, treated, and then returned to the phreatic zone. These "pump-and-treat", or above-ground, methods are extremely expensive. On the other hand, known in situ water treatment devices may employ air lift pumping as a means of producing gas bubbles to remove VOCs. The theory is that gas is pumped into the wells which causes water and subsequently formed gas bubbles to rise upward. VOCs are transferred from the contaminated water to the gas bubbles which can then be collected for treatment. However, known in situ water treatment devices may not result in rapid vapor saturation which results in a slow and inefficient process. Vapor saturation occurs when the rising bubbles become saturated with VOC vapor. Therefore, there is a need for the development of an improved in situ gas sparging remediation method for removing contaminants in an inexpensive and more efficient manner.
The present invention involves new concepts for in-well removal of contaminants from the saturation zone. It avoids expensive "above ground" remediation methods, and provides a more efficient method of gas sparging than recently developed in situ remediation methods. The present invention is an in-well air stripping and adsorption technique designed to provide inexpensive, efficient gas sparging. The injected gas may be air or any specific or combination of gases such as carbon monoxide. In addition, the injected gas may be at any temperature.